I 



CHEMICAL ANALYSIS 



29 



In dry countries the sewage is often very concentrated. An 

 example that I received in 1901 from Bloemfontein, Orange 

 Colony,! contained, in parts per 100,000, 5,256 of total solids, of 

 which 4,212 were organic; the oxygen consumed was 1131*2, 

 the organic nitrogen 457*1, ammoniacal nitrogen 537*6, and 

 chlorine 273*6. 



To take a fair average sample of raw sewage in a bottle is 

 obviously hopeless, owing to the large pieces of solid matter that 

 at intervals come down. The only thing to be done is to roughly 

 strain the sample for analysis, and to ascertain on a larger scale 

 the amount and nature of the solids. 



Opinions on sewages and effluents must be based on a number 

 of examinations extending over several days and embracing 

 every hour of the day. At the same time, opportunity must be 

 given for immediate analyses simultaneously, as delay produces 

 change. I will give an example of the procedure by which I 

 attained this in October, i8gg. A strong sewage was gauged 

 every half-hour, and a sample collected in cubic centimetres 

 proportional to the number of gallons flowing ; these half-hourly 

 samples were at once poured into a large vessel, and at the end 

 of three hours were thoroughly mixed, and the average of the 

 six samples taken in a stoppered glass bottle for analysis. The 

 results and the times are given below, and it will be seen 



Parts per 100,000. 



Nitrites and nitrates were only present in traces. 



^ Journal of the Sanitary Institute, xxiv., part i., p. 116. 



